Percussion mechanism

ABSTRACT

The fluid-actuated percussion mechanism includes a housing with an internalylindrical space wherein a reciprocating piston, which divides the space into a working stroke chamber and an idle stroke chamber, is received. The mechanism further includes fluid distributing means and a distribution unit mounted in the housing for placing the chambers and a source of the working fluid in communication. The housing also accommodates a work-performing member adapted to receive impacts from the piston. The distribution unit includes at the inlet of at least one of the chambers a valve made in the form of a resilient annular element. The surface of the distribution unit has valve seats made in it, the number of which corresponds to that of the inlets for supplying the working fluid into the chambers. The resilient valve element is taut about the surface of the distribution unit in opposition to the inlets and encircles the periphery of the unit. The internal surface of the resilient element with the valve seat and the external surface of the resilient element with the housing each define at least one inlet passage for supplying the working fluid to the inlets. 
     The disclosed structure of the valve, of the distribution unit and of the housing enables an increase in the total flow area of the passages through which the working fluid is supplied to the inlets of the chambers and thus an increase in the power output of the percussion mechanism.

FIELD OF THE INVENTION

The present invention relates to percussion mechanisms and, moreparticularly, it relates to percussion mechanisms actuated by a fluidunder pressure, e.g. compressed air or compressed steam.

The invention can be utilized to utmost effectiveness in percussionmechanisms used in mining and like tools, e.g. in percussion drillssubmergible in a borehole, portable pneumatic drills, air hammers.

The invention can be also used in construction tools, e.g. inpneumatically actuated pile drivers, in self-propelled earth drills fordriving underground holes, in concrete-breaking tools, etc.

Further, the present invention can be utilized for improving percussivetools used in machine-building, e.g. cutting and riveting tools, tampingtools, etc.

BACKGROUND OF THE INVENTION

Known in the art is a percussion mechanism which includes a housing withan internal space wherein there is received a reciprocable piston whichdivides this internal space into a working stroke chamber and an idlestroke chamber. The housing of the mechanism is made in the form of aseries combination of a cylinder, a fluid-distribution unit and aconnection for connecting the mechanism to a source of pressurizedfluid. A socket is made in the cylinder at the side of the free end,which accomodates a work-performing member, and an exhaust port is madecentrally of the cylinder. The working stroke chamber includes acounterbore made in the internal surface of the cylinder, which isadjacent to the distribution unit.

The piston of the mechanism has a blind central bore wherein there isreceived a tube fixed in the distribution unit with aid of a couplingsleeve. The internal surface of the central bore of the piston has madetherein an annular passage which communicates via an inclined passagewith the idle stroke chamber. The bottom zone of this bore freelycommunicates via a lateral passage with the exterior of the piston,which engages the internal surface of the cylinder. The distributionunit, the tube and the coupling sleeve jointly define a valve spaceaccommodating a valve member made in the form of an elastic bush havinga seat-engaging shoulder on the internal side of the bush, thisseat-engaging shoulder adjoining the base of the bush, facing thepiston. The external lateral surface of the elastic bush and theinternal lateral surface of the distribution unit define therebetween anannular inlet slit. This inlet slit communicates on one side thereof,through openings of the distribution unit, with the working strokechamber of the mechanism, and on the other side communicates via thevalve space and the lateral openings in the bush with a supply spacedefined within the bush. Also communicating with the supply space of thebush is the axial passage of the tube received in the piston.

Upon the abovedescribed pneumatic percussion mechanism having beenconnected via the connection member to a source of pressurized fluid,the fluid fills the supply space and from there flows via the lateralopenings in the bush and the valve space, the inlet slit of the valve,the openings of the distribution unit, the working or forward strokechamber and the exhaust port into the ambient atmosphere, while it flowsvia the tube, the annular passage and the inclined passage into the idlestroke chamber. Under the action of the pressure differential in thevalve space and in the working stroke chamber, the elastic bush isspread to close the inlet slit.

The working fluid that has filled the working stroke chamber iswithdrawn through the exhaust port into the ambient air, while the idlestroke chamber is being filled with the pressurized working fluid,whereby the piston is driven through the idle or return stroke. As thetube closes off the annular passage of the piston, the supply of theworking fluid is cut off, and as the piston by its further motion clearsthe exhaust port, the fluid escapes through the exhaust port. By thistime the lateral passage of the piston aligns with the annularcounterbore of the cylinder, through which the pressurized working fluidenters the working stroke chamber from the central bore of the piston,thus filling this chamber. The pressure drop across the elastic bush,i.e. the difference between the pressures acting upon the external andinternal lateral surfaces thereof, decreases and, when it falls to apredetermined value, the inherent resilience of the elastic bushcontracts the bush, whereby the inlet slit becomes open. The pressurewithin the working stroke chamber becomes equal to that in the supplyspace. The piston first halts, and then is driven through a workingstroke. When the internal surface of the cylinder closes off the lateralpassage in the piston, the working stroke chamber remains incommunication with the supply space exclusively via the valve. As thepiston moves further on, it clears the exhaust port, and the pressure inthe forward or working stroke chamber drops. The pressure differentialexpands the valve to close off the inlet slit, and the working fluidescapes from the working chamber. By this moment the tube opens theannular passage of the piston, and the pressurized working fluid fillsthe idle stroke chamber. Following an impact against the work-performingmember, the piston is driven through an idle stroke.

A disadvantage of the abovedescribed pneumatic percussion mechanismhaving its valve made in the form of an elastic bush with an internalseat-engaging shoulder is that the valve defines with the distributionunit only one inlet slit. This hampers the feed of a substantial amountof the working fluid into the chamber of the mechanism, and thus affectsthe energy of the impact and the output capacity of the mechanism. If itis necessary to increase the pressure in other chambers of themechanism, e.g. in the idle stroke chamber, it would require as manyvalves as there are chambers into which the pressurized fluid is to beadditionally supplied. This would complicate the design of the mechanismand impair its reliability.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate the abovementioneddisadvantages of the hitherto known percussion mechanisms.

It is also an object of the present invention to increase the poweroutput of a percussion mechanism, with a simultaneous reduction of thespecific consumption of the pressurized working fluid.

It is another object of the present invention to simplify the structureof the percussion mechanism.

It is still another object of the present invention to enhance thereliability of the performance of the percussion mechanism.

It is yet another object of the present invention to provide apercussion mechanism with an increased flow passage area of its passagesthrough which the pressurized fluid is fed into the chamber of themechanism, without increasing the specific consumption of thepressurized fluid.

These and other objects are attained in a percussion mechanism actuatedby a pressurized fluid, which comprises a housing with an internalcylindrical space wherein there is received an axially reciprocablepiston which divides the internal space of the housing into a workingstroke chamber of a variable volume and an idle stroke chamber of avariable volume. The chamber in the internal cylindrical spacecommunicates through fluid distributing means and a distribution unitsituated in the housing on the working stroke chamber side with a sourceof the pressurized fluid, at least one of these chambers having a valvedisposed on the distribution unit through which the pressurized fluid isfed to effect reciprocation of the piston for the piston to deliverimpacts upon a work-performing member accommodated in the housing. Inaccordance with the present invention, the valve includes a resilientannular valve element, with valve seats being made on the surface of thedistribution unit, their number equalling that of the inlet openings forsupplying the fluid into the chambers, the annular resilient valveelement being taut about the distribution unit in opposition to the saidinlet openings and encircling the distribution unit about its periphery.The internal surface of the resilient element with the seat and itsexternal surface with the housing each defines at least one inletpassage for supplying the fluid to the said inlets.

The abovespecified structure of the valve of the distribution unit andof the housing provides a passage for supplying the fluid to the saidinlets at both end faces of the valve, and thus increases the total flowarea of these passages.

It is preferable that the inlet passages for supplying the pressurizedfluid to the inlets of the seats and of the distribution unit should bemade in the form of longitudinal recesses in the surface of thedistribution unit. This enables the resilient element of the valve tomove circumferentially relative to the inlets in the course of theservice of the mechanism and enhances the reliability of the mechanism.

In case of percussion mechanisms designed for relatively short serviceperiods, it is preferable that the inlet passages for supplying thepressurized fluid to the inlets of the seat and of the distribution unitshould be made in the form of longitudinal recesses or grooves made inthe internal surface of the resilient element, in areas facing theinlets. In this way the construction of the distribution unit and of thepercussion mechanism, as a whole, can be simplified.

In percussion mechanisms in which the resilient valve element is of astructure permitting mere bending of the element, it is preferable thatthe inlets for supplying the pressurized fluid into the chamber shouldbe arranged in diametral opposition to each other. When the valve isused for supplying the fluid into the working stroke chamber and intothe idle stroke chamber, it is expedient that the respective axes ofeach pair of said inlets should be perpendicular. In this way thestability of the operating motion of the valve is enhanced, as is thereliability of its performance.

In percussion mechanism in which the distribution unit supporting theresilient valve element has additional passages for supplying thepressurized fluid into the chambers of the mechanism, it is preferablethat the resilient valve element should be made in the form of an openring having its ends fixed to the valve seat. This feature simplifiesthe construction of the percussion mechanism and increases itsreliability.

It is also preferable that the external or peripheral surface of theresilient element should be of an increased thickness in areas opposingthe inlets of the seat, to prevent excessive pressing-in of theresilient valve element and thus to enhance its durability.

It is further preferable that the external surface of the resilientvalve element should have, in areas facing the inlets of thedistribution unit, recesses or grooves shaped like these inlets, butbeing slightly larger than the inlets. This feature saves the resilientvalve element from being damaged by the edges of these inlets and thusincreases its useful life.

It is likewise preferable that the surface of the distribution unitshould have abutment means or lugs adapted to accommodate the resilientvalve element therebetween, to preclude longitudinal displacement of theelement and thus to increase the reliability of its performance.

It is preferable that in percussion mechanisms wherein the resilientvalve element is of a structure defining its substantially bendingdeformation, the resilient element should be taut about detachablefastening means mounted on the distribution unit. In this case thesefastening means can be made of a material with a relatively high viscousor internal friction, so as to dampen high-frequency oscillation of theresilient valve element in operation and thus to enhance itsreliability.

In some precussion mechanisms it may be preferable that the distributionunit receiving thereabout the resilient valve element should have acylindrical bore and should be mounted so that the internal surface ofthis bore should present a continuation of the internal cylindricalspace of the housing. This feature reduces the overall length of thepercussion mechanism and simplifies its structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in connection with its perferredembodiments, with reference being had to the accompanying drawings,wherein:

FIG. 1 is a longitudinal cross sectional view of a percussion mechanismembodying the invention, wherein the valve is adapted to supply theworking fluid into the working stroke chamber;

FIG. 2 is a cross-sectional view across the inlet of the chamber of anembodiment of the valve having several inlets;

FIG. 3 is a cross-sectional view across the inlet of the chamber ofanother embodiment of the percussion mechanism wherein the inletpassages are defined by longitudinal recesses in the internal surface ofthe resilient valve element;

FIG. 4 is a longitudinal cross sectional view of a percussion mechanismwherein the surface of the cylindrical bore of the distribution unit isa continuation of the surface of the internal cylindrical space of thehousing;

FIG. 5 is a cross sectional view taken along the line V--V of FIG. 4;

FIG. 6 is a longitudinal cross sectional view of a percussion mechanismwherein the resilient valve element is adapted to control the supply ofthe pressurized fluid into the working stroke chamber and into the idlestroke chamber;

FIG. 7 is a cross-sectional view across the inlet of the chamber in anembodiment with two side passages;

FIG. 8 is a cross sectional view taken along the line VIII--VIII of FIG.7;

FIG. 9 is a longitudinal cross sectional view of a percussion mechanismwherein the resilient valve element is in the form of an open ring;

FIG. 10 is a cross sectional view taken along the line X--X of FIG. 9;

FIG. 11 is a cross sectional view across the inlet of the chamber ofanother embodiment of the percussion mechanism;

FIG. 12 is a cross sectional longitudinal view of a percussion mechanismwherein the inlets of the distribution unit, adapted to supply theworking fluid into one of the chambers of the mechanism, are arranged inopposition to one another, this view having been taken along the lineXII--XII of FIG. 13;

FIG. 13 is a cross sectional view taken on line XIII--XIII of FIG. 12;and

FIG. 14 is a cross sectional view taken along the line XIV--XIV of FIG.13.

DETAILED DESCRIPTION OF THE INVENTION

A deep-hole pneumatic drill for drilling blast holes can incorporate apercussion mechanism constructed in accordance with the presentinvention and illustrated in FIG. 1, which increases the power output ofthe drill.

The hollow housing 1 (FIG. 1) of the mechanism receives thereinside areciprocating piston 2 which divides the internal space of the housing 1into a working stroke chamber 3 and an idle stroke chamber 4. Thehousing 1 is provided with a distribution unit 5 with a valve seat 6provided thereon and also with a connection means 7 for connection ofthe mechanism to a source of a pressurized working fluid (the source notbeing shown in the drawings). Adjacent to its free end, the housing 1has a socket 8 which accomodates a work-performing member 9. Made in thecentral portion of the housing 1 are through-going exhaust ports 10 and11 for withdrawal of the working fluid from the aforementioned chambers3 and 4 of the mechanism. The piston 2 is provided with a through axialbore 12 which in its central part widens into a space 13. This axialbore 12 of the piston 2 receives a distributing rod 14 fixed in thedistribution unit 5 and having a blind axial bore 15 opening at one ofits end into a supply space 16 defined within the distribution unit 5and having its blind end communicating via a radial opening 17 with theinternal space 13 of the piston 2. The free end of the distributing rod14 is provided with a stem 18 adapted to close the bore 12 of the piston2. In the central part of the distributing rod 14 there is made anexternal passage 19 in the form of a groove, for establishingcommunication between the working stroke chamber 3 and the space 13,when the piston 2 is most remote from the work-performing member 9.Defined between the housing 1 and the distribution unit 5 is a valvespace 20 communicating via a lateral passage 21 with the supply space16. Made in the side surface of the distribution unit 5 are longitudinalrecesses 22 including inlets 23 opening into the working stroke chamber3. Received about the side surface of the distribution unit 5, inopposition to these inlets 23, is a taut resilient annular valve element24 defining with these recesses 22 inlet passages 25 whose ends openinto the valve space 20 and whose central part opens into the inlets 23.The provision of the inlet passages 25 at both end faces of theresilient valve element 24 increases the total flow area of the valve.The external surface of the resilient valve element 24 has in areasopposing the inlets 23 thickened portions 26 adapted to preventexcessive pressing-in of the resilient element 24 into the inlets 23 inoperation. To preclude longitudinal displacement of the resilient valveelement 24, lugs 27 are provided on the surface of the distribution unit5. The valve element can be made of commonly available grades ofoil-proof rubber.

In another preferred embodiment of the invention, the distribution unit5' (FIG. 2) has several inlets 23 arranged, preferably, in diamteralopposition to one another, as it is shown in FIG. 2. This increases thestability of the operation-wise motion of the resilient valve element24.

Percussion mechanisms embodying the present invention and designed forrelatively short service periods, preferably have their inlet passages25 (FIG. 3), for supplying the pressurized fluid to the inlets 23 of thedistribution unit 5", include longitudinal recesses 28 in the internalsurface of the resilient valve element 29 in the areas facing the inlets23. This simplifies the construction of the distribution unit 5" and ofthe percussion mechanism, as a whole. In this case the resilient element29 is retained against displacement relative to the distribution unit5".

When the percussion mechanism is connected via the connection 7 (FIG. 1)to the source of pressurized fluid, the fluid fills the supply space 16and flows therefrom via the lateral passage 21, the valve space 20, theinlet passages 25, the inlets 23, the working stroke chamber 3 andexhaust port 10 into the ambient air and via the axial bore 15, theradial opening 17 and the space 13 into the bore 12. Owing to thepressure drop between the valve space 20 and the working stroke chamber3, the portions of the resilient valve element 24, opposing the inlets23, are deformed to close the inlet passages 25. Therefore, the supplyof the pressurized fluid into the working stroke chamber 3 is cut off,while the working fluid that has found its way into the working strokechamber 3 escapes via the port 10. By this time the pressurized fluidhas found its way from the bore 12 of the piston 2 through gaps betweenthe piston 2 and the work-performing member 9 into the idle strokechamber 4 and has filled it. The piston 2 is thus driven off thework-performing member 9, and the axial bore 12 thereof becomes fullyopen. The pressure in the idle stroke chamber 4 is rapidly built up, andthe piston 2 is driven through its idle stroke. Upon the stem 18 closingthe bore 12, the supply of the working fluid into the idle strokechamber 4 is cut off, and the further motion of the piston 2 makes thepiston 2 clear the exhaust port 11, whereby the working fluid iswithdrawn into the ambient air. As the piston 2 moves further on, itsinternal space 13 becomes connected via the external passage 19 to theworking stroke chamber 3, whereby the working fluid fills the workingstroke chamber 3. The pressure differential between the valve space 20and the working stroke chamber 3 decreases, and, when it falls to apredetermined value, the portions of the resilient valve element 24,which have been pressed against the inlets 23, straighten up by theirown inherent resilience, whereby the inlet passages 25 become open. Thepressure in the working stroke chamber 3 rapidly increases to that inthe supply space 16, whereby the piston 2 is first halted, and thendriven through a working stroke. When the external passage 19 clears theinternal space 13 of the piston 2, the working stroke chamber 3 remainsin communication with the supply space 16. The great flow area of theinlet passages 25 providing for a high working pressure in the workingstroke chamber 3. Upon the closure stem 18 having left the bore 12, theworking fluid begins filling the idle stroke chamber 4, and practicallyat the same moment the piston 2 begins to open the exhaust port 10. Theflow rate of the working fluid through the inlet passages 25 increasesto a critical value, the condition of the resilient valve element 24becomes unstable, and the ensuing slight drop of the pressure in theworking stroke chamber 3 result in an abrupt increase of the pressuredifferential between the valve space 20 and the working stroke chamber3. This can be explained by the fact that by this moment the inflow ofthe working fluid into the valve space 20 becomes higher than the flowrate of the fluid through the inlet passages 25, whereby the pressurewithin the valve space 20 becomes equal to that in the supply space 16.The small mass of the resilient valve element 24 and the relativelygreat area of this element 24, acted upon by the said pressuredifferential, are responsible for the resilient valve element 24 rapidlyclosing off the inlet passages 25. The working fluid then escapesthrough the exhaust port 10 and the piston 2 delivers an impact upon thework-performing member 9 and thereafter is driven through an idlestroke.

Then the piston 2 is repeatedly driven through cycles similar to theabovedescribed one.

The present invention is also embodied in the percussion mechanismillustrated in FIGS. 4 and 5 of the drawings. This embodiment isparticularly suitable for incorporation is pneumatic concrete breakersand pick hammers.

The internal space of the housing 30 (FIG. 4) having exhaust ports 31,32 receives therein a reciprocating piston 33 which divides this spaceinto a working stroke chamber 34 and an idle stroke chamber 35.

The housing 30 is provided adjacent to the idle stroke chamber 35 with asocket 36 accommodating a work-performing member 37, and the end of thehousing 30 adjacent to the working stroke chamber 34 is closed with alid 38 (FIGS. 4 and 5), which is provided with a connection 39 forconnecting the mechanism to a source (not shown) of a working fluidunder pressure. On the face thereof, adjacent to the working strokechamber 34 (FIG. 4), the lid 38 is provided with a cylindrical lug 40supporting thereon a distributing rod 41 having an axial bore (a groove)42, a radial opening 43, an external passage 44 and a stem 45.

Received between the housing 30 and the lid 38 is a distribution unit 46having stretched thereabout, in opposition to inlets 47, an annularresilient valve element 48, e.g. made of rubber (see FIG. 5). Thedistribution unit 46 defines with the lid 38 a distribution or supplyspace 49 communicating via a passage 50 provided in the lid 38 with theaxial bore 42 of the distributing rod 41, the supply space alsocommunicating with the connection 39.

The cylindrical bore 51 of the distribution unit 46 has a diameterslightly greater than that of the piston 33, whereby the piston partlyenters the distribution unit 46 at the end of its idle stroke. In somemodifications it may be found structurally advisable to have thedistribution unit 46 integral with the housing 30.

The above described general layout of the percussion mechanism enables areduction in its overall length and simplification of its construction.

The operation of the percussion mechanism described hereinabove issimilar to that of the mechanism illustrated in and described inconnection with FIG. 1, and, therefore, it will not be separatelydescribed.

In applications requiring a relatively long piston stroke and limitedconsumption of the pressurized working fluid, it may be found preferableto use the embodiment of the percussion mechanism illustrated in FIG. 6.

The hollow housing 52 (FIG. 6) of this mechanism supports therein adistribution unit 53 and receives a reciprocating piston 54 dividing theinternal space of the housing 52 into a working stroke chamber 55 and anidle stroke chamber 56. The housing 52 is provided with a socket 57accommodating a work-performing member 58 and has exhaust ports 59 and60. The housing 52 may have made in the wall thereof either two sidepassages 61, 62 (FIG. 7), for supplying the working fluid into the idlestroke chamber 56, or a single passage 61 (FIG. 6). Defined between thehousing 52 and the distribution unit 53 is a valve space 63communicating via openings 64 with a supply space 65. The distributionunit 53 is provided with valve seats 66 and a connection 67 forconnecting the percussion mechanism to a source (not shown) of thepressurized working fluid. Made in the side surface of the distributionunit 53 of the presently described embodiment is either a singlelongitudinal recess 68 or several such recesses 68, 69, 70 (FIG. 7), thedepth of the recess 68 being somewhat smaller than that of the recesses69. The recesses 68 and 69 have opening thereinto inlets 71 forsupplying the pressurized working fluid into the working stroke chamber55 (FIG. 6), whereas the recess 70 (FIGS. 7 and 8) has no such inlet.The internal surface of the housing 52 has made therein a longitudinalrecess 72 communicating with the side passage 62. Received about theside surface of the distribution unit 53, in opposition to the inlet ofthe passage 61 and to the inlet or inlets leading into the chamber 55,is a taut annular resilient valve element 73 (FIG. 6) or an element 74(FIGS. 7 and 8) defining with the respective inlets either an inletpassage 75 (FIG. 6) or a plurality of such passages 75, 76, 77 (FIG. 7)opening at both ends thereof into the valve space 63. Another inletpassage 78 is defined by the longitudinal recess or groove made in theexternal surface of the resilient element, respectively, 73 (FIG. 6) or74 (FIG. 7), in opposition to the inlet of the passage 61. To protectthe resilient valve element 74 from being forced into the inlet of thepassage 62, the resilient element 74 has made therein a recess 79 havingat the inlet thereof a shape similar to that of the inlet of the passage62, although of a somewhat greater size. The resilient element 73 (FIG.6) is retained against longitudinal displacement by projections 80provided on the distribution unit 53.

The material of the resilient valve element 73 or 74 (FIGS. 7, 8) of thepresently described emobodiment can be any common grade or oil-proofrubber.

As the presently described percussion mechanism is connected via theconnection 67 (FIG. 6) to a source of the pressurized working fluid, thefluid flows via the supply space 65 and the openings 64 into the valvespace 63, wherefrom it flows via the inlet passage 75 into the workingstroke chamber 55 and escapes via the exhaust port 59 into the ambientatmosphere, the working fluid also flows either via the inlet passage 78and the side passage 61, or via the inlet passages 77, 78 and the sidepassages 61, 62 (FIG. 7), into the idle stroke chamber 56 (FIG. 6).Owing to the pressure differential between the valve space 63 and theworking stroke chamber 55, the portion of the resilient valve element73, opposing the inlet 71, is deformed to close the inlet passage 75,the flow area of the inlet passage 78 increasing. The modification ofthe present embodiment, having the distribution unit 53 with the sidepassages 61, 62 and the resilient element 74, as illustrated in FIGS. 7and 8, operates in a manner similar to that being described herein belowfor the operation of the mechanism illustrated in FIG. 6. The pressureof the working fluid in the idle stroke chamber 56 drives the piston 54through an idle stroke. The idle stroke chamber 56 remains communicatedwith the valve space 63 via the inlet passage 78, whereby the pressurein this chamber 56 rapidly drops. Meanwhile, the pressure in the workingstroke chamber 55 increases, owing to the working fluid being compressedtherein. When the pressure differential between the working strokechamber 55 and the inlet passage 78 attains a predetermined value, theportion of the resilient valve element 73, defining the last-mentionedpassage, is displaced toward the inlet of the side passage 61, closingthe passage 61 and simultaneously opening the inlet passage 75 throughwhich the pressurized working fluid begins to flow into the workingstroke chamber 55. The supply of the pressurized working fluid into theidle stroke chamber 56 is thus discontinued, and eventually the workingfluid is withdrawn from the idle stroke chamber 56 into the ambientatmosphere.

Meanwhile, the pressure in the working stroke chamber 55 is increasing,whereas the pressure differential between the valve space 63 and thelast-mentioned chamber 55 is decreasing.

Upon the said pressure differential falling to a predetermined value,the portions of the resilient valve element 73, pressed against therecesses 69 (FIG. 7), straighten up by their inherent resilience andthus open the inlet passages 76. The pressure in the working strokechamber 55 (FIG. 6) rapidly increases. The piston 54 is first halted,and then driven through a working stroke. At the initial moment ofopening by the piston 54 of the exhaust ports 59 the rate of flow of theworking fluid through the inlet passages 76 attains a critical value,which results in these passages being swiftly closed. The working strokechamber 55 remains in communication with the valve space 63 via theinlet passage 75, and the pressure in this chamber rapidly drops. In themeantime, the pressure in the idle stroke chamber 56 increases, owing tothe working fluid therein being compressed by the moving piston 54,whereby the portion of the resilient valve element 73, opposing thelongitudinal recess 68, is displaced to close the passage 75 and to openthe inlet passage 78. The pressure in the idle stroke chamber 56 rapidlyincreases. The piston delivers an impact upon the work-performingmember, and thereafter is driven through an idle stroke.

Then the piston is driven repeatedly through cycles similar to thatdescribed hereinabove.

A specific attractive feature of the operation of the modification ofthe presently described embodiment of the invention, illustrated in FIG.7, is that one portion of the resilient valve element 74, viz. theportion defining the inlet passages 75 and 78 which have relativelysmall flow areas, controls the operation of other portions of thisresilient valve element 74, defining the inlet passages 76 ofsubstantially greater flow areas or cross-sections. This enables anincrease in the power output of the percussion mechanism with a moderateconsumption of the working fluid.

Another embodiment of the present invention is illustrated in FIG. 9 ofthe drawings. The general layout of this modification is particularlysuitable for incorporation in hand-operated pneumatic percussion tools,e.g. concrete breakers.

The hollow housing 81 has mounted therein a distribution unit 82 and isclosed with a lid 83, the housing 81 receiving therein a reciprocatingpiston 84 which divides the internal space of the housing 81 into aworking stroke chamber 85 and an idle stroke chamber 86. The housing 81has made therethrough exhaust ports 87, 88 for withdrawal of the workingfluid from the chambers and has a socket 89 accommodating awork-performing member 90. The piston 84 has a head 91 and a tail 92 andis provided with a blind axial bore 93 opening to the side surface ofthe tail 92 via a radial passage 94 and serving to supply the workingfluid into the idle stroke chamber 86. The tail 92 of the piston 84 hasmade in the surface thereof an external passage (a groove) 95 forsupplying the pressurized working fluid into the working stroke chamber85 when the piston 84 is at its most remote point from thework-performing member 90. The lid 83 is provided with a connection forconnecting the mechanism to a source (not shown) of the pressurizedworking fluid and defines with the distribution unit 82 a supply space96. The distribution unit 82 has a central bore 97 adapted to receivethe tail 92 of the piston 84. The internal wall of this bore includes anannular counterbore 98 opened into the supply space 96 via a passage 99.The central bore 97 of the distribution unit 82 and the working strokechamber 85 are interconnected with a longitudinal passage 100.

The external side surface of the distribution unit 82 is provided with aplurality of valve seats in the form of longitudinal recesses 101including inlets 102 opening into the longitudinal passages 100.Received about the external side surface of the distribution unit 82 isa resilient valve element 103 stretched tight and being made in the formof an open or split ring having its ends fixed in the distribution unit82. The material of the resilient valve element 103 may be any suitablecommon grade of oil-proof rubber. The resilient valve element 103defines with the longitudinal recesses 101 inlet passages 104. Thisresilient element 103 it is retained against longitudinal displacementby lugs 105. The means fastening the ends of the resilient valve element103 include plugs 106 (FIG. 10) provided on these ends of the resilientelement 103 and received, in association with expanding pins 107, inholes 108 provided for the purpose in the body of the distribution unit82. Another modification of the means fastening the resilient element103 is illustrated in FIG. 11, the resilient valve element 103 of thismodification having lugs 109 receivable in longitudinal grooves 110 inthe body of the distribution unit 82.

Upon the percussion mechanism of the presently described embodimentbeing connected to a source of the pressurized working fluid, the fluidflows into the supply space 96 (FIG. 9), to flow therefrom via the inletpassages 104, inlets 102, longitudinal passages 100, the working strokechamber 85 and the exhaust port 87 into the ambient atmosphere, and toflow via the passage 99, the annular counterbore 98 and the radialpassage 94 into the axial bore 93. Owing to the pressure differentialbetween the supply space 96 and the working stroke chamber 85, theportions of the resilient valve element 103, disposed in opposition tothe inlets 102, are deformed to close the inlet passages 104. Therebythe supply of the working fluid into the working stroke chamber 85 iscut off, while the working fluid that has already flown into thelast-mentioned chamber is withdrawn into the ambient atmosphere throughthe exhaust port 87. Under the action of the pressurized working fluidin the axial bore 93, the piston 84 is driven off the work-performingmember 90, whereby this bore 93 completely opens to supply the workingfluid into the idle stroke chamber 86. The piston is driven through anidle stroke. Upon the tail 92 of the piston 84 closing off thecounterbore 98, the supply of the working fluid into the chamber 86 isdiscontinued, and as the piston 84 moves further on, its head 91 clearsthe exhaust port 88, whereby the working fluid is withdrawn from theidle stroke chamber 86 into the ambient atmosphere. When the externalpassage 95 aligns with the annular counter 98, the working fluid issupplied into the working stroke chamber 85 and into the central bore97. The pressure differential between the supply space 96 and theworking stroke chamber 85 decreases, and the portions of the resilientvalve element 103, opposing the inlets 102, straighten up by their owninherent resilience, to open the inlet passages 104. The pressure in theworking stroke chamber 85 and in the central bore 97 rapidly increases.The piston 84 is first halted, and then is driven through a workingstroke. Upon the external passage 95 clearing the counterbore 98, theworking stroke chamber 85 and the central bore 97 remain incommunication with the supply space 96 only through the valve. At theinitial moment of the opening of the exhaust port 87 by the head 91 ofthe piston 84, the rate of flow of the working fluid through the inletpassages attains a critical value, and the ensuing slight displacementof the piston 84 results in a rapid increase of the pressuredifferential acting upon the resilient valve element 103, whereby theresilient valve element 103 swiftly closes the inlet passages 104. Thesupply of the working fluid into the working stroke chamber 85 and intothe central bore 97 is thus discontinued, and the working fluid iswithdrawn through the exhaust port 87. With the radial passage 94aligning with the annular counterbore 98, the working fluid is suppliedinto the idle stroke chamber 86. Following an impact against thework-performing member 90, the piston 84 is driven through an idlestroke, whereafter the abovedescribed cycle is repeated.

Still another embodiment of the present invention is illustrated in FIG.12 of the drawing. This general layout of a percussion mechanism isparticularly suitable for incorporation in metal-cutting and rivetinghammers.

The hollow housing 111 (FIG. 12) of the mechanism receives therein areciprocating piston 112 which divides the internal space of the housing111 into a working stroke chamber 113 and an idle stroke chamber 114.The housing 111 has made through its wall exhaust ports 115, 116 forwithdrawal of the working fluid from the said chambers and has a socket117 adapted for accommodation of a work-performing member 118. Thehousing 111 has made therein side passages 119 for supplying thepressurized working fluid into the idle stroke chamber 114. The end ofthe housing 111, adjoining the working-stroke chamber 113, is closedwith a lid 120 incorporating a connection 121 for connecting thepercussion mechanism with a source (not shown) of the pressurizedworking fluid. The housing 111 has mounted therein a distribution unit123 with inlets 124, 125. Two inlets 124 are arranged in opposition toeach other and open into the working stroke chamber 113, and the othertwo inlets 125 are arranged in opposition to each other and open intothe side passages 119, the respective axes of the inlets 124 and 125being perpendicular (see FIG. 13). Mounted externally of thedistribution unit 123 on removable fastening means 126 (FIG. 13) is anannular resilient valve element 127 defining with the distribution unit123 inlet passages 128 and 129. The fastening means 126 has lugs 130(FIG. 14) retaining the resilient valve element 127 against longitudinaldisplacement. In some modifications of the percussion mechanism it maybe preferable to have the removable fastening means in the form ofrolling bodies. The material of the valve element of the presentlydescribed embodiment may be spring steel, some grades of bronze or toughplastic (e.g. "Kapralon"). To enhance reliability, the exterior of thevalve element is preferably coated with an elastic material, e.g.rubber.

When the percussion mechanism is connected via the connection 121 (FIG.12) with a source of the pressurized working fluid, the fluid flows intothe supply space 122 and therefrom through the inlet passages 128,inlets 124, working stroke chamber 113 and exhaust port 115 into theambient atmosphere, and flows via the inlet passages 129, inlets 125 andside passages 119 into the idle stroke chamber 114. Under the action ofthe pressure differential, the portions of the resilient valve element127 (FIG. 13), opposing the inlets 124, are deformed and pressed tightagainst these inlets. With the inlets 124 being arranged in diametralopposition to each other, and the material of the valve element beingrelatively rigid, this deformation results in the shape of the resilientelement 127 becoming elliptical.

The portions of the resilient valve element 127, opposing the other pairof inlets 125, are thus displaced toward the housing 111, whereby theflow area of the inlet passages 129 increases. Under the influence ofthe pressure in the idle stroke chamber 114 (FIG. 12), the piston 112 isdriven through an idle stroke. At the initial moment of the opening ofthe exhaust port 116 by the piston 112, the flow rate of the workingfluid through the inlet passages 129 attains the critical value, and theensuing slight displacement of the piston 112 results in an abruptincrease of the pressure differential acting upon the portions of theresilient valve element 127, opposing the inlets 125 (FIG. 13), wherebythese portions of the resilient valve element 127 are deformed andpressed tight against the inlets 125. Meanwhile, the portions of theresilient valve element 127, which have been pressed against the inlets124, clear these inlets 124 by the action of the inherent resilience ofthe element 127 and of the pressure of the working fluid in the workingstroke chamber 113, owing to the working fluid being compressed by themoving piston 112, whereby the inlet passages 128 become open. Thepressure in the working stroke chamber 113 (FIG. 12) increases, whilethe working fluid escapes from the idle stroke chamber 114 into theambient atmosphere. The piston 112 is first halted, and then is driventhrough a working stroke. At the initial moment of the opening of theexhaust port 115 by the piston 112, the flow rate of the working fluidthrough the inlet passages 128 attains a critical value, and the ensuingslight further motion of the piston 112 results in the pressuredifferential acting upon the portions of the resilient valve element127, opposing the inlets 124 (FIG. 13), abruptly increasing. Theportions of the resilient valve element 127 are deformed and pressedagainst the inlets 124. At the same instant the portions of theresilient valve element 127, which have been pressed against the inlets125, clear these inlets 125 by the action of the inherent resilience ofthe material of the element 127 and of the pressure of the working fluidin the idle stroke chamber 114. The pressure in the idle stroke chamber114 increases, while the working fluid is withdrawn from the workingstroke chamber 113 through the exhaust port 115. Upon having deliveredan impact upon the work-performing member 118, the piston 112 is driventhrough an idle stroke. Then the piston 112 is repeatedly driven throughcycles similar to the abovedescribed one.

The last-described construction of the percussion mechanism enablesutilization of the resilience of the resilient valve element 127 toestablish a feedback connection between the feed of the pressurizedworking fluid into the working stroke chamber 113 and the feed of saidfluid into the idle stroke chamber 114. This enhances the reliability ofthe performance of the valve and provides for timely discontinuation ofthe supply of the working fluid into these chambers.

What we claim is:
 1. A percussion mechanism actuated by a pressurizedfluid supplied from a source of pressurized fluid, comprising a housing(1) with an internal cylindrical space and exhaust ports (10, 11);afluid actuated piston (2) positioned for axial reciprocation in saidspace of said housing and dividing said space into a working strokechamber (3) of a variation volume and an idle stroke chamber (4) of avariable volume, and each of said chambers communicating with one ofsaid exhaust ports; fluid distributing means (5) including pressureresponsive surfaces (24) adapted to create passages (25, 23) fordistributing the fluid into said working stroke chamber (3) of themechanism; a distribution unit (14), having inlet means (15) fordistributing the fluid into at least one of said chambers (3, 4),accommodated in said housing (1) adjacent to said working stroke chamber(3) and being in mutual cooperative association with said fluiddistributing means (5) and said piston for establishing means ofcommunication (17, 19) between said chambers (3, 4) and the source ofpressurized fluid; a work-performing member (9) accommodated in saidhousing (1) to receive impacts from said piston (2) reciprocated by theaction of the fluid; said surfaces (24) being carried by said fluiddistribution means (5) and including a resilient annular valve element(24); valve seats (6) provided in a surface of said fluid distributionmeans (5), their number equalling that of the passage means (23) of saidfluid distribution means (5), said resilient annular valve element (24)being stretched tight about the surface of said fluid distribution means(5) in opposition to said passage means (23) and encircling said fluiddistribution means (5) about its periphery, an internal surface of saidresilient annular valve element (24) with said valve seat (6) definingat least inlet one passage (25) for controlling fluid flow about saidfluid distributing means (5), whereby said portion is repeatedly drivenup and down in said housing by the action of said fluid flowing into andout of said chambers and said exhaust ports via said inlet means andsaid passage means.
 2. A percussion mechanism as set forth in claim 1,wherein the gaseous passages for supplying the gaseous fluid underpressure to inlets provided in said fluid distributing means includelongitudinal recesses made in the surface of said distributing means. 3.A percussion mechanism as set forth in claim 1, wherein the gaseouspassages for supplying the gaseous fluid under pressure include said atleast one inlet passage and a longitudinal recess made in the internalsurface of said resilient annular valve element in the areas opposingeach said inlet.
 4. A percussion mechanism as set forth in claim 1,including a plurality of inlets in said distributing means for supplyingthe fluid arranged in diametral opposition to one another.
 5. Apercussion mechanism as set forth in claim 1, wherein said annularresilient valve element is in the form of an open ring having its endfastened to said distributing means.
 6. A percussion mechanism as setforth in claim 1, wherein an external surface of said resilient valveelement, in the areas opposing inlets provided in said distributingmeans, has thickened portions to protect said resilient valve elementfrom damage.
 7. A percussion mechanism as set forth in claim 2, whereinan external surface of said resilient valve element in the areas,opposing the inlets provided in said distributing means, has recesses.8. A percussion mechanism as set forth in claim 1, wherein lug means areprovided on the surface of said distributing means to accommodate saidresilient valve element therebetween, said lug means retaining saidresilient valve element against longitudinal displacement.
 9. Apercussion mechanism as set forth in claim 1, wherein said resilientvalve element is stretched tight about removable fastening means mountedon said distributing means.
 10. A percussion mechanism as set forth inclaim 1, wherein said distributing means has a cylindrical bore and ismounted on said housing so that an internal surface of said bore is acontinuation of an internal surface of said cylindrical space of saidhousing.
 11. A percussion mechanism actuated by a pressurized fluidsupplied from a source of pressurized fluid, comprising a housing (1)with an internal cylindrical space and exhaust ports (10, 11);a fluidactuated piston (2) positioned for axial reciprocation in said space ofsaid housing and dividing said space into a working stroke chamber (3)of a variable volume and an idle stroke chamber (4) of a variablevolume, and each of said chambers communicating with one of said exhaustports; a fluid distributing unit (5) having at least one inlet (23) fordistributing the fluid into said chamber; a distribution rod (14),having a blind bore (15) communicating with said source of pressurizedfluid, fixedly secured to said fluid distributing unit and accommodatedin said housing adjacent to said working stroke chamber to establish,with said fluid distributing unit, communication between said chambersand the source of pressurized fluid; said distribution rod having anopening (17) adjacent to the bottom of said blind bore and an externalgrooved passageway (19) adjacent said fluid distributing unit; awork-performing member (9) accommodated in said housing to receiveimpacts from said piston reciprocated by the action of the fluid; valvemeans carried by said distribution unit and disposed about said inletand including a resilient annular valve element (24); valve seats (6)provided on an external surface of said distribution unit (5), theirnumber equalling that of the at least one inlet supplying the fluid,said resilient annular valve element (24) being stretched tight aboutthe surface of said distribution unit (5) in opposition to said at leastone inlet and encircling said distribution unit about its periphery, aninternal surface of said resilient annular valve element with said valveseat defining at least one passage for supplying the fluid to saidinlet.